Mid-Latitude Weather Hazards

While tropical storms dominate hazard headlines, the mid-latitudes (broadly 30–60 degrees N and S) experience a wide range of severe weather hazards. These include extratropical storms, tornadoes, heatwaves, cold spells, and extreme precipitation events. The UK, situated between 50–60 degrees N, is particularly affected by mid-latitude weather systems. Understanding these hazards requires knowledge of the polar jet stream, Rossby waves, depressions, anticyclones and their associated weather patterns.

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Mid-Latitude Depressions (Extratropical Cyclones)

Key Definition: A mid-latitude depression is a low-pressure weather system that forms at the polar front, where warm subtropical air meets cold polar air. Depressions are the primary weather-producing systems in the mid-latitudes.

Formation (Cyclogenesis)

Mid-latitude depressions form through the process of cyclogenesis at the polar front, as described by the Norwegian Polar Front Model (Bjerknes and Solberg, 1922):